A "firewall for" is something one needed with Windows XP and earlier, as in "a piece of software that acted as a firewall".
Nowadays, both Windows 7+ and Linux come with a built-in firewall, that one might want a "GUI for {}'s firewall".
One of such GUIs, is TinyWall, that is also FOSS (GPLv3). I see people have suggested some more.
To be precise, all these options are inferior in functionality to firewalls like ZoneAlarm... but since you're asking for a non-tech friendly solution, they should be adequate.